CN111740165A

CN111740165A - Electrolyte solution, electrochemical device containing electrolyte solution, and electronic device

Info

Publication number: CN111740165A
Application number: CN202010595886.4A
Authority: CN
Inventors: 许艳艳; 郑建明; 徐春瑞; 韩翔龙
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Xiamen Xinneng'an Technology Co ltd
Priority date: 2020-06-28
Filing date: 2020-06-28
Publication date: 2020-10-02
Anticipated expiration: 2040-06-28
Also published as: CN111740165B

Abstract

The present application relates to an electrolyte solution including an additive a and a heterocyclic compound, and an electrochemical device and an electronic device including the electrolyte solution. The electrochemical device of the present application, including the electrolyte, has significantly improved high-temperature cycle performance and high-temperature storage performance.

Description

Electrolyte solution, electrochemical device containing electrolyte solution, and electronic device

Technical Field

The present disclosure relates to the field of energy storage technologies, and more particularly, to an electrolyte, and an electrochemical device and an electronic device including the electrolyte.

Background

In order to overcome the increasingly serious global energy shortage in terms of environmental protection, the dependence on non-renewable energy sources must be greatly reduced. Great efforts should be made to efficiently convert, store, transport and harvest renewable energy sources such as wind, solar and tidal currents. Rechargeable Lithium Ion Batteries (LIBs) are considered to be one of the most attractive energy storage systems due to high energy density and relatively simple reaction mechanism, high operating voltage, long lifetime, green environmental protection. Nowadays, lithium ion batteries have been widely used in various fields, from such as electronic products as cameras, digital cameras, 3C consumer electronics, to stationary energy storage systems and transportation vehicles including Hybrid Electric Vehicles (HEV), Plug Hybrid Electric Vehicles (PHEV), and Electric Vehicles (EVS). Lithium ion batteries generally consist of a positive electrode, a negative electrode, a separator and an electrolyte. The anode comprises an anode active material, the anode active material mainly comprises a lithium-containing metal compound, and the lithium manganate has a three-dimensional tunnel structure and excellent lithium removal property, is rich in resources, low in price, good in safety, easy to synthesize, non-toxic and environment-friendly, and is one of materials most suitable for being used as the anode. However, lithium manganate has a serious capacity fading problem, and especially under high temperature conditions, the main reasons for capacity fading are: Jahn-Teller effect, dissolution of transition metal, decomposition of electrolyte to generate gas and the like, so that the problem of capacity attenuation of the lithium manganate can be improved from the aspects of appearance control, surface coating, element doping, electrolyte optimization and the like of the positive active material.

The electrolyte is used as an important key material, plays a role in transferring lithium ions in front of a positive electrode and a negative electrode, and is an important guarantee for obtaining the performances of high energy, high multiplying power, long circulation, high safety and the like of the battery. A general commercialized electrolyte includes an organic solvent, an additive, and a lithium salt. The additive has various types and remarkable effects, becomes a key factor for improving the performance of the battery, is difficult to form stable interface protection by a single additive, and has larger film forming resistance along with the increase of the adding amount. Therefore, the electrolyte formula provided by the application can reduce high-temperature gas generation of the lithium manganate battery, does not deteriorate impedance, and further has excellent high-temperature and low-temperature performances.

Disclosure of Invention

The present application provides an electrolyte and an electrochemical device including the electrolyte, in an attempt to solve at least one of the problems existing in the related art to at least some extent.

The application provides an electrolyte containing an additive A and a heterocyclic compound, which can effectively improve the cycle capacity retention rate of an electrochemical device, reduce gas generation in the cycle process and improve the high-temperature storage performance.

According to an embodiment of the present application, there is provided an electrolyte comprising an additive a and a heterocyclic compound represented by formula I

Wherein R is₁And R₂Each independently selected from substituted or unsubstituted C₁To C₆Alkylene or substituted or unsubstituted C₂To C₆Alkenylene, wherein when substituted, the substituent is at least one of halogen, cyano or phenyl; wherein the additive A comprises at least one compound of formula II, formula III, formula IV or formula V:

wherein R is₃Is substituted or unsubstituted C₁To C₆Wherein when substituted, the substituent is halogen; wherein R is₄、R₅、R₆、R₇、R₈、R₉、R₁₀Each independently selected from hydrogen, halogen, substituted or unsubstituted C₁To C₆Alkyl, substituted or unsubstituted C₂To C₆Alkenyl, substituted or unsubstituted C₂To C₆Alkynyl, substituted or unsubstituted C₆To C₁₀Aryl, wherein when substituted, the substituent is halogen; wherein m is 1 to 6.

According to embodiments of the present application, the heterocyclic compound comprises:

at least one of; wherein the additive A comprises at least one of methylene methanedisulfonate, propenyl-1, 3-sultone, 1, 3-propanesultone, 1, 3-propanedisulfonic anhydride, or 1, 4-butanesultone; it is composed ofBased on the weight of the electrolyte, the weight percentage of the heterocyclic compound is 0.01-6%, and the weight percentage of the additive A is 0.01-6%.

According to the embodiment of the application, the weight percentage of the additive A is alpha percent and the weight percentage of the heterocyclic compound is beta percent based on the weight of the electrolyte, and the requirements of 0.02 to 10 of alpha + beta and 20 of alpha/beta are met.

According to an embodiment of the present application, wherein the electrolyte further comprises at least one of an additive B, an additive C, an additive D, an additive E, or an additive F, wherein the additive B comprises at least one of vinylene carbonate, fluoroethylene ester, vinyl ethylene carbonate, 1, 3-dioxane, 1, 4-dioxane, or dioxolane; wherein the additive C is vinyl sulfate; wherein the additive D comprises at least one of succinonitrile, glutaronitrile, adiponitrile, 2-methyleneglutaronitrile, dipropylacrylonitrile, 1,3, 6-hexanetricarbonitrile, 1,2, 6-hexanetricarbonitrile, 1,3, 5-pentanedinitrile, 1, 2-bis (cyanoethoxy) ethane, or ethoxy (pentafluoro) cyclotriphosphazene; wherein the additive E comprises one of lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium bisthiooxalato borate, lithium difluorooxalato borate, lithium difluorophosphate, lithium tetrafluoroborate, or lithium 2-trifluoromethyl-4, 5-dicyanoimidazorate; wherein the additive F comprises at least one of succinic anhydride, glutaric anhydride, citraconic anhydride, maleic anhydride, methylsuccinic anhydride, 2, 3-dimethylmaleic anhydride or trifluoromethylmaleic anhydride, wherein the weight percentage of the additive B is 0.01-15%, the weight percentage of the additive C is 0.01-5%, the weight percentage of the additive D is 0.1-10%, the weight percentage of the additive E is 0.01-5%, and the weight percentage of the additive F is 0.01-5%, based on the weight of the electrolyte.

According to an embodiment of the present application, the electrolyte further includes a cyclic ester and a chain ester in a weight ratio of 1:9 to 7:3, wherein the cyclic ester includes at least one of ethylene carbonate, propylene carbonate, γ -butyrolactone, ethylene carbonate substituted with a fluorine-containing group, or propylene carbonate substituted with a fluorine-containing group; wherein the chain ester comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, fluoro ethyl methyl carbonate or fluoro ethyl propionate.

According to an embodiment of the present application, there is provided an electrochemical device including a positive electrode including a positive active material layer including a positive active material and a positive current collector; and any of the above electrolytes.

According to an embodiment of the present application, in the electrochemical device, the electrolyte further includes Mn²⁺Wherein the Mn is based on the weight of the electrolyte²⁺The weight percentage of (B) is less than or equal to 2000 ppm.

According to the embodiment of the present application, in the electrochemical device, the liquid retention amount of the electrolyte is 0.5g/Ah to 5 g/Ah.

According to an embodiment of the present application, in the electrochemical device, the sum X% of the weight percentages of the heterocyclic compound and the additive a and the specific surface area Y m of the positive electrode active material²The ratio of/g satisfies 0.01-7.5 of X/Y.

According to the embodiment of the application, the positive active material layer comprises first particles, the positive electrode is perpendicular to the cross section of the current collector by adopting a scanning electron microscope test, the spherical gray scale of the first particles is more than or equal to 115RGB, and the cross sectional area of the first particles is less than 20 μm²The area of the first particles accounts for 5 to 50% of the cross-sectional area of the positive electrode active material layer.

According to the embodiment of the application, the positive active material layer contains second particles, the positive electrode is perpendicular to the cross section of the current collector by adopting a scanning electron microscope test, the spherical gray scale of the second particles is less than 115RGB, and the cross sectional area of the second particles is greater than 20 μm²The area of the second particles accounts for 5 to 50% of the cross-sectional area of the positive electrode active material layer.

According to an embodiment of the present application, in the electrochemical device, the first particles include Li_aNi_xCo_yMn_zM_mO₂Wherein a is more than or equal to 0.9 and less than or equal to 1.2, x is more than or equal to 0.3 and less than or equal to 1, Y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, x + Y + z is more than or equal to 1, and M is more than 0 and less than or equal to 0.1, and the M element comprises at least one of Al, Ti, W, Zr, Nb, In, Ru, Sb, Sr, Y and F; the second particles contain Li_bMn_2-jMe_jO₄Wherein a is more than or equal to 0.9 and less than or equal to 1.2, j is more than 0 and less than 0.1, and the Me element comprises at least one of Mg, Ti, Cr, Al, B, Fe, Zr, Na and S.

According to an embodiment of the present application, in an electrochemical device, wherein a doping amount W of Me is 0% < W < 0.7% based on the weight of the positive electrode active material.

According to an embodiment of the present application, there is provided an electronic device including any one of the electrochemical devices described above.

Additional aspects and advantages of embodiments of the present application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the present application.

Drawings

Drawings necessary for describing embodiments of the present application or the prior art will be briefly described below in order to describe the embodiments of the present application. It is to be understood that the drawings in the following description are only some of the embodiments of the present application. It will be apparent to those skilled in the art that other embodiments of the drawings can be obtained from the structures illustrated in these drawings without the need for inventive work.

FIG. 1 is a scanning electron micrograph of a cross section of a positive electrode according to an example of the present application.

Detailed Description

Embodiments of the present application will be described in detail below. The embodiments described herein are illustrative and are provided to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application.

As used herein, the terms "substantially", "substantially" and "about" are used to describe and illustrate minor variations. When used in conjunction with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely as well as instances where the event or circumstance occurs in close proximity. For example, when used in conjunction with numerical values, the term can refer to a range of variation that is less than or equal to ± 10% of the stated numerical value, such as less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%. For example, two numerical values are considered to be "substantially" identical if the difference between the two numerical values is less than or equal to ± 10% (e.g., less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%) of the mean of the values.

Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity, and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.

In the detailed description and claims, a list of items linked by the term "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means a only; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item A may comprise a single component or multiple components. Item B may comprise a single component or multiple components. Item C may comprise a single component or multiple components.

The term "alkyl" is intended to be a straight chain saturated hydrocarbon structure having from 1 to 20 carbon atoms. "alkyl" is also contemplated to be a branched or cyclic hydrocarbon structure having from 3 to 20 carbon atoms. For example, the alkyl group may be an alkyl group of 1 to 20 carbon atoms, an alkyl group of 1 to 10 carbon atoms, an alkyl group of 1 to 5 carbon atoms, an alkyl group of 5 to 20 carbon atoms, an alkyl group of 5 to 15 carbon atoms, or an alkyl group of 5 to 10 carbon atoms. When an alkyl group having a particular carbon number is specified, all geometric isomers having that carbon number are intended to be encompassed; thus, for example, "butyl" is meant to include n-butyl, sec-butyl, isobutyl, tert-butyl, and cyclobutyl; "propyl" includes n-propyl, isopropyl and cyclopropyl. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl, and the like. In addition, the alkyl group may be optionally substituted.

The term "alkylene" alone or as part of another substituent means a divalent radical derived from an alkyl group.

The term "alkenyl" refers to a monovalent unsaturated hydrocarbon group that can be straight or branched chain and has at least one and typically 1,2, or 3 carbon-carbon double bonds. Unless otherwise defined, the alkenyl group typically contains 2 to 20 carbon atoms, and may be, for example, an alkenyl group of 2 to 20 carbon atoms, an alkenyl group of 6 to 20 carbon atoms, an alkenyl group of 2 to 10 carbon atoms, or an alkenyl group of 2 to 6 carbon atoms. Representative alkenyl groups include, by way of example, ethenyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like. In addition, the alkenyl group may be optionally substituted.

The term "alkenylene" encompasses both straight-chain and branched alkenylene groups. When an alkenylene group having a particular carbon number is specified, all geometric isomers having that carbon number are intended to be encompassed. For example, the alkenylene group may be an alkenylene group of 2 to 20 carbon atoms, an alkenylene group of 2 to 15 carbon atoms, an alkenylene group of 2 to 10 carbon atoms, an alkenylene group of 2 to 5 carbon atoms, an alkenylene group of 5 to 20 carbon atoms, an alkenylene group of 5 to 15 carbon atoms, or an alkenylene group of 5 to 10 carbon atoms. Representative alkylene groups include, for example, ethenylene, propenylene, butenylene, and the like. In addition, alkenylene may be optionally substituted.

The term "alkynyl" refers to a monovalent unsaturated hydrocarbon group that can be straight-chain or branched and has at least one, and typically 1,2, or 3 carbon-carbon triple bonds. Unless otherwise defined, the alkynyl group typically contains 2 to 20 carbon atoms, and may be, for example, an alkynyl group of 2 to 20 carbon atoms, an alkynyl group of 6 to 20 carbon atoms, an alkynyl group of 2 to 10 carbon atoms, or an alkynyl group of 2 to 6 carbon atoms. Representative alkynyl groups include, for example, ethynyl, prop-2-ynyl (n-propynyl), n-but-2-ynyl, n-hex-3-ynyl, and the like. In addition, the alkynyl group may be optionally substituted.

The term "aryl" encompasses monocyclic and polycyclic ring systems. Polycyclic rings can have two or more rings in which two carbons are common to two adjoining rings (the rings are "fused"), wherein at least one of the rings is aromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryls, heterocyclics, and/or heteroaryls. For example, the aryl group may be C₆To C₅₀Aryl radical, C₆To C₄₀Aryl radical, C₆To C₃₀Aryl radical, C₆To C₂₀Aryl or C₆To C₁₀And (4) an aryl group. Representative aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl, and naphthalen-1-yl, naphthalen-2-yl, and the like. In addition, the aryl group may be optionally substituted.

As used herein, the term "halogen" may be F, Cl, Br or I.

When the above substituents are substituted, the substituents may be selected from the group consisting of: halogen, alkyl, cycloalkyl, alkenyl, aryl and heteroaryl.

Embodiments of the present application provide an electrolyte and an electrochemical device and an electronic device including the same. In some embodiments, the electrochemical device is a lithium ion battery.

First, electrolyte

Embodiments of the present application provide an electrolyte including an organic solvent, an electrolyte, and an additive including an additive a and a heterocyclic compound. In some embodiments, the electrolyte is a nonaqueous electrolyte.

The additive A and the heterocyclic compound are added into the electrolyte, so that the circulating capacity retention rate of the electrochemical device can be effectively improved, the gas generation problem in the circulating process can be reduced, and the high-temperature storage performance can be improved. The reason is that the heterocyclic compound and the additive A can form a Solid Electrolyte Interface (SEI) film with lower impedance under the combined action to protect a negative electrode interface, so that the high-temperature cycle performance is improved; the film can be formed on the anode, so that the contact between the anode and electrolyte is reduced, the stability of the anode is improved, and the high-temperature storage performance is improved. In the electrolyte, the additive A and the heterocyclic compound act synergistically, so that the high-temperature storage performance of the electrochemical device can be improved, and meanwhile, the high-temperature cycle performance of the electrochemical device can be effectively improved, and the problem of gas storage and generation of the electrochemical device can be reduced.

Heterocyclic compounds

In some embodiments, the heterocyclic compound comprises a compound of formula I

In the formula I, R₁And R₂Each independently selected from substituted or unsubstituted C₁To C₆Alkylene or substituted or unsubstituted C₂To C₆Alkenylene, wherein when substituted, the substituent is at least one of halogen, cyano or phenyl.

In some embodiments, the heterocyclic compound comprises:

at least one of (1).

In some embodiments, the heterocyclic compound is present in an amount of 0.01% to 6% by weight based on the weight of the electrolyte. In some embodiments, the weight percent of heterocyclic compound is about 0.01%, about 0.05%, about 0.1%, about 0.3%, about 0.5%, about 0.8%, about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, 0.01% -1%, 0.1% -1%, 0.5% -5%, 1% -3%, 1% -5%, 2% -5%, or 2% -6%, etc., based on the weight of the electrolyte.

Additive A

In some embodiments, additive a comprises at least one of the compounds of formula II, formula III, formula IV, or formula V:

in formula II, R₃Is substituted or unsubstituted C₁To C₆Wherein when substituted, the substituent is halogen. In the formulae III, IV and V, R₄、R₅、R₆、R₇、R₈、R₉、R₁₀Each independently selected from hydrogen, halogen, substituted or unsubstituted C₁To C₆Alkyl, substituted or unsubstituted C₂To C₆Alkenyl, substituted or unsubstituted C₂To C₆Alkynyl, substituted or unsubstituted C₆To C₁₀Aryl, wherein when substituted, the substituent is halogen; wherein m is 1 to 6.

In some embodiments, additive a comprises at least one of Methylene Methanedisulfonate (MMDS), propenyl-1, 3-sultone (PES), 1, 3-Propanesultone (PS), 1, 3-Propanedisulfonic Anhydride (PA), or 1, 4-Butanesultone (BS).

In some embodiments, the weight percent of additive a is 0.01% to 6% based on the weight of the electrolyte. In some embodiments, the weight percent of additive a is about 0.01%, about 0.05%, about 0.1%, about 0.3%, about 0.5%, about 0.9%, about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, 0.01% -1%, 0.1% -1%, 0.5% -5%, 1% -3%, 1% -5%, 2% -5%, or 3% -6%, etc., based on the weight of the electrolyte.

In some embodiments, the weight percent of the additive A is alpha percent and the weight percent of the heterocyclic compound is beta percent based on the weight of the electrolyte, and the alpha + beta is more than or equal to 0.02 and less than or equal to 10, and the alpha/beta is more than or equal to 0.01 and less than or equal to 20. In some embodiments, the weight percent of the additive A is alpha percent and the weight percent of the heterocyclic compound is beta percent based on the weight of the electrolyte, and the requirements of 0.1 to alpha plus beta to 8 and 0.01 to alpha/beta to 20 are met. The additive a and the heterocyclic compound in the range enable more effective improvement of the overall performance of the electrochemical device.

Other additives

In some embodiments, the electrolyte may further include at least one of an additive B, an additive C, an additive D, an additive E, or an additive F, in addition to the heterocyclic compound and the additive a.

In some embodiments, additive B comprises at least one of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), Vinyl Ethylene Carbonate (VEC), 1, 3-dioxane, 1, 4-dioxane, or dioxolane. In some embodiments, the additive B is present in an amount of 0.01% to 15% by weight, based on the weight of the electrolyte. In some embodiments, the weight percentage of additive B is about 0.01%, about 0.05%, about 0.1%, about 0.2%, about 0.5%, about 0.8%, about 1%, about 1.2%, about 1.4%, about 1.8%, about 2%, about 3%, about 4%, about 5%, about 8%, about 10%, about 12%, about 15%, 0.01% -5%, 0.1% -6%, 1% -8%, 1% -10%, 2% -10%, or 5% -15%, etc., based on the weight of the electrolyte.

In some embodiments, additive C is vinyl sulfate (DTD). In some embodiments, the weight percentage of additive C is 0.01% to 5% based on the weight of the electrolyte. In some embodiments, the weight percent of additive C is about 0.01%, about 0.05%, about 0.1%, about 0.2%, about 0.5%, about 0.8%, about 1%, about 1.2%, about 1.4%, about 1.8%, about 2%, about 3%, about 4%, about 5%, 0.01% -1%, 0.1% -2%, 1% -5%, or 2% -5%, etc., based on the weight of the electrolyte.

In some embodiments, the additive D comprises at least one of succinonitrile, glutaronitrile, adiponitrile, 2-methyleneglutaronitrile, dipropylacrylonitrile, 1,3, 6-hexanetrinitrile, 1,2, 6-hexanetrinitrile, 1,3, 5-pentanetrinitrile, 1, 2-bis (cyanoethoxy) ethane, or ethoxy (pentafluoro) cyclotriphosphazene. In some embodiments, the additive D is present in an amount of 0.01% to 10% by weight, based on the weight of the electrolyte. In some embodiments, the weight percentage of additive D is about 0.01%, about 0.05%, about 0.1%, about 0.2%, about 0.5%, about 0.8%, about 1%, about 1.2%, about 1.4%, about 1.8%, about 2%, about 3%, about 4%, about 5%, about 8%, about 10%, 0.01% -5%, 0.1% -7%, 1% -8%, 1% -9%, or 2% -9%, etc., based on the weight of the electrolyte.

In some embodiments, the additive E comprises one of lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium bisthalite borate, lithium difluorooxalate borate, lithium difluorophosphate (LiDFP), lithium tetrafluoroborate, or lithium 2-trifluoromethyl-4, 5-dicyanoimidazolium. In some embodiments, the additive E is present in an amount of 0.01% to 5% by weight, based on the weight of the electrolyte. In some embodiments, the weight percent of additive E is about 0.01%, about 0.05%, about 0.1%, about 0.2%, about 0.5%, about 0.8%, about 1%, about 1.2%, about 1.4%, about 1.8%, about 2%, about 3%, about 4%, about 5%, 0.01% -0.5%, 0.01% -1%, 0.01% -2%, 0.1% -3%, or 0.1% -5%, etc., based on the weight of the electrolyte.

In some embodiments, the additive F comprises at least one of succinic anhydride, glutaric anhydride, citraconic anhydride, maleic anhydride, methylsuccinic anhydride, 2, 3-dimethylmaleic anhydride, or trifluoromethylmaleic anhydride. In some embodiments, the additive F is present in an amount of 0.01% to 5% by weight, based on the weight of the electrolyte. In some embodiments, the weight percentage of the additive F is about 0.01%, about 0.05%, about 0.1%, about 0.2%, about 0.5%, about 0.8%, about 1%, about 1.2%, about 1.4%, about 1.8%, about 2%, about 3%, about 4%, about 5%, 0.01% -1%, 0.1% -2%, 1% -5%, or 2% -5%, etc., based on the weight of the electrolyte.

In some embodiments, the sum of the weight percentages of additive B and additive D is 4.5% to 15% based on the weight of the electrolyte.

In some embodiments, the electrolyte further comprises a non-aqueous organic solvent, wherein the non-aqueous organic solvent comprises a cyclic ester and a chain ester, and the weight ratio of the cyclic ester to the chain ester is 1:9 to 7: 3. In some embodiments, the cyclic ester comprises at least one of ethylene carbonate, propylene carbonate, γ -butyrolactone, ethylene carbonate substituted with a fluorine-containing group, or propylene carbonate substituted with a fluorine-containing group. In some embodiments, the chain ester comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, fluoroethyl methyl carbonate, or ethyl fluoropropionate.

In some embodiments, the electrolyte further comprises at least one of a lithium salt, a sodium salt, or a potassium salt.

In some embodiments, the lithium salt comprises lithium hexafluorophosphate (LiPF)₆) Lithium bistrifluoromethanesulfonylimide (LiN (CF)₃SO₂)₂) Lithium bis (fluorosulfonyl) imide (LiN (SO)₂F)₂) Lithium bis (oxalato) borate (LiB (C)₂O₄)₂) Lithium difluorooxalato borate (LiBF)₂(C₂O₄) Lithium hexafluoroarsenate (LiAsF)₆) Lithium perchlorate (LiClO)₄) Or lithium trifluoromethanesulfonate (LiCF)₃SO₃) At least one of (1). In some embodiments, the concentration of the lithium salt in the electrolyte is from 0.5mol/L to 1.5 mol/L. In some embodiments, the concentration of the lithium salt in the electrolyte is about 0.5mol/L, about 0.8mol/L, about 1.2mol/L, about 1.5mol/L, 0.5mol/L-1mol/L, 0.8mol/L-1.2mol/L, or 1mol/L-1.5mol/L, and the like.

In some embodiments, the sodium salt comprises sodium hexafluorophosphate (NaPF)₆) Sodium bistrifluoromethanesulfonylimide (NaN (CF)₃SO₂)₂) Bis (fluorosulfonyl) imide sodium (NaN (SO)₂F)₂) Sodium bisoxalato (NaB (C))₂O₄)₂) Sodium difluorooxalate (NaBF)₂(C₂O₄) Sodium hexafluoroarsenate (NaAsF)₆) Sodium perchlorate (NaClO)₄) Or trifluoromethanesulfonic acidSodium (NaCF)₃SO₃) At least one of (1). In some embodiments, the concentration of the sodium salt in the electrolyte is 0.5mol/L to 1.5 mol/L. In some embodiments, the concentration of the sodium salt in the electrolyte is about 0.5mol/L, about 0.8mol/L, about 1.2mol/L, about 1.5mol/L, 0.5mol/L-1mol/L, 0.8mol/L-1.2mol/L, or 1mol/L-1.5mol/L, and the like.

In some embodiments, the potassium salt comprises potassium hexafluorophosphate (KPF)₆) Potassium bistrifluoromethanesulfonylimide (KN (CF)₃SO₂)₂) Potassium bis (fluorosulfonyl) imide (KN (SO)₂F)₂) Potassium bis (oxalato) borate (KB (C)₂O₄)₂) Potassium difluorooxalato borate (KBF)₂(C₂O₄) Potassium hexafluoroarsenate (KAsF)₆) Potassium perchlorate (KClO)₄) Or potassium trifluoromethanesulfonate (KCF)₃SO₃) In some embodiments, the concentration of the potassium salt in the electrolyte is from 0.5mol/L to 1.5 mol/L. In some embodiments, the concentration of the potassium salt in the electrolyte is about 0.5mol/L, about 0.8mol/L, about 1.2mol/L, about 1.5mol/L, 0.5mol/L-1mol/L, 0.8mol/L-1.2mol/L, or 1mol/L-1.5mol/L, and the like.

Two, electrochemical device

Embodiments of the present application also provide an electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolyte of the present application. The electrochemical device of the present application may include any device in which electrochemical reactions occur, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. In some embodiments, the electrochemical device of the present application includes a positive electrode having a positive electrode active material capable of occluding and releasing metal ions; a negative electrode having a negative electrode active material capable of occluding and releasing metal ions; a separator interposed between the positive electrode and the negative electrode; and an electrolyte of the present application. In some embodiments, the electrochemical device may be a pouch cell, a cylindrical cell, or a prismatic cell.

Electrolyte solution

The electrolyte used in the electrochemical device of the present application is any of the electrolytes described above in the present application. In addition, the electrolyte used in the electrochemical device of the present application may further include other electrolytes within a range not departing from the gist of the present application.

In some embodiments, the electrolyte further comprises Mn (PF)₆)₂Wherein Mn (PF) is based on the weight of the electrolyte₆)₂The weight percentage of (B) is less than or equal to 2000 ppm. In some embodiments, Mn (PF) based on the weight of the electrolyte₆)₂Less than or equal to about 2000ppm, about 1500ppm, about 1000ppm, about 500ppm, about 200ppm, about 100ppm, about 80ppm, about 50ppm, about 20ppm, or about 10ppm, etc.

Mn (PF) in electrolyte₆)₂Can further improve the high-temperature cycle performance and the high-temperature storage performance of the electrochemical device, mainly because the electrolyte forms good interface protection on the surface of the cathode active material, and Mn in the electrolyte²⁺Can further inhibit the dissolution of lithium manganate Mn²⁺The destruction of the negative electrode is suppressed due to the formation of a better SEI film at the time of deposition of the negative electrode. Mn (PF) in electrolyte₆)₂Can be obtained by adding Mn (PF)₆)₂Or from an electrolyte.

In some embodiments, the electrolyte has a retention of 0.5g/Ah to 5 g/Ah. In some embodiments, the electrolyte has a retention capacity of about 0.5g/Ah, about 1g/Ah, about 1.5g/Ah, about 2g/Ah, about 2.5g/Ah, about 3g/Ah, about 3.5g/Ah, about 4.0g/Ah, about 5.0g/Ah, 0.5g/Ah-1.0g/Ah, 1g/Ah-2.0g/Ah, 1g/Ah-5.0g/Ah, or 2g/Ah-5.0g/Ah, and the like.

Positive electrode

In some embodiments, the positive electrode includes a positive active material layer including a positive active material, and a positive current collector.

In some embodiments, the sum X% of the weight percentages of the heterocyclic compound and additive a and the specific surface area Y m of the positive electrode active material²The ratio of/g satisfies 0.01-7.5 of X/Y. In some embodiments, the value of X/Y may be about 0.05, about 0.1, about 0.5, about 1, about 1.5, about2. About 2.5, about 3, about 3.5, about 4, about 4.5, about 5, about 5.5, about 6, about 6.5, about 7, or about 7.5, etc.

As shown in fig. 1, the positive electrode of the present example was tested using a scanning electron microscope for a cross section perpendicular to the current collector, and the positive active material layer included a current collector 1, first particles 2 and second particles 3, which had different spherical grayscales and cross-sectional areas.

In some embodiments, the first particles have a spherical gray of 115RGB or more, and a cross-sectional area of less than 20 μm²The total area of the first particles is 5% to 50% based on the cross-sectional area of the positive electrode active material layer.

In some embodiments, the first particles comprise Li_aNi_xCo_yMn_zM_mO₂Wherein a is more than or equal to 0.9 and less than or equal to 1.2, x is more than or equal to 0.3 and less than or equal to 1, Y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, x + Y + z is more than or equal to 1, and M is more than 0 and less than or equal to 0.1, and the M element contains at least one of Al, Ti, W, Zr, Nb, In, Ru, Sb, Sr, Y and F.

In some embodiments, the positive active material layer comprises second particles, the positive electrode is perpendicular to the cross section of the current collector tested by a scanning electron microscope, the spherical gray scale of the second particles is less than 115RGB, and the cross section area of the second particles is more than 20 μm²The total area of the second particles is 5% to 50% in terms of the cross-sectional area of the positive electrode active material layer.

In some embodiments, the second particles comprise Li_bMn_2-jMe_jO₄Wherein B is more than or equal to 0.9 and less than or equal to 1.2, j is more than 0 and less than 0.1, and the Me element comprises at least one of Mg, Ti, Cr, Al, B, Fe, Zr, Na and S.

In some embodiments, a scanning electron microscope is adopted to test a cross section of the positive electrode perpendicular to the current collector, and the current collector has an area accounting for 5% -20% of the area of the cross section of the positive electrode active material layer.

In some embodiments, the porosity of the positive electrode active material layer is 8% to 25%.

The positive active material layer further includes a binder, and optionally a conductive material. The binder improves the binding of the positive electrode active material particles to each other, and also improves the binding of the positive electrode active material to the current collector.

In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy, nylon, and the like.

In some embodiments, the conductive material includes, but is not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from the group consisting of metal powder, metal fiber, copper, nickel, aluminum, silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

In some embodiments, the current collector may be, but is not limited to, aluminum.

The positive electrode may be prepared by a preparation method well known in the art. For example, the positive electrode can be obtained by: the positive active material composition is prepared by mixing a positive active material, a conductive material, and a binder in a solvent, and coating the positive active material composition on a current collector. In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone, and the like.

In some embodiments, the positive electrode is made by forming a positive electrode material on a current collector using a positive electrode active material layer including a lithium transition metal-based compound powder and a binder.

In some embodiments, the positive active material layer may be generally fabricated by: the positive electrode active material and a binder (a conductive material, a thickener, and the like, which are used as needed) are dry-mixed to form a sheet, and the obtained sheet is pressure-bonded to a positive electrode current collector, or these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried. In some embodiments, the material of the positive electrode active material layer includes any material known in the art.

Negative electrode

In some embodiments, the negative electrode comprises a negative active material comprising natural graphite, artificial graphite, mesophase micro carbon spheres, hard carbon, soft carbon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO₂Spinel-structured lithiated TiO₂-Li₄Ti₅O₁₂Or a Li-Al alloy.

In some embodiments, the electrochemical device is a lithium ion secondary battery. In order to prevent unintentional precipitation of lithium metal on the anode during charging, the electrochemical equivalent of the anode active material capable of intercalating and extracting lithium ions is preferably larger than that of the cathode. Therefore, the amounts of the positive electrode active material and the negative electrode active material need to be adjusted accordingly to obtain a high energy density. In some embodiments, the ratio of the anode capacity to the cathode capacity may be 1.01 to 1.2.

Isolation film

In some embodiments, the electrochemical device of the present application is provided with a separator between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separation film used in the electrochemical device of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance or the like formed of a material stable to the electrolyte of the present application.

For example, the release film may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.

At least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.

The inorganic layer comprises inorganic particles and a binder, wherein the inorganic particles are selected from one or more of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is selected from one or a combination of more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer comprises a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).

In some embodiments, the present application provides a lithium ion battery comprising the above-described positive electrode, negative electrode, separator, and electrolyte, the electrolyte being any of the electrolytes described previously herein.

In some embodiments, the present application also provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, an electrolyte, and a packaging foil; the positive electrode comprises a positive current collector and a positive film layer coated on the positive current collector; the negative electrode comprises a negative electrode current collector and a negative electrode film layer coated on the negative electrode current collector; the electrolyte is any one of the electrolytes described in the application.

Electronic device

The electrochemical device of the present application has excellent high-temperature cycle properties and high-temperature storage properties, so that the electrochemical device manufactured thereby is suitable for electronic devices in various fields.

The use of the electrochemical device of the present application is not particularly limited, and it may be used for any use known in the art. In one embodiment, the electrochemical device of the present application can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headphones, video recorders, liquid crystal televisions, portable cleaners, portable CDs, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game machines, clocks, power tools, flashlights, cameras, household large batteries, lithium ion capacitors, and the like.

Fourth, example

The following describes performance evaluation according to examples and comparative examples of lithium ion batteries of the present application. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application.

Preparation of lithium ion battery

(1) Preparation of the Positive electrode

Preparing positive electrode active material nickel cobalt lithium manganate (LiNi)_0.5Co_0.2Mn_0.3O₂Abbreviated as NCM), lithium manganate (LiMn)₂O₄Abbreviated as LMO) are mixed according to a certain mass ratio (the mass ratio of the embodiment 1 to the embodiment 44 is 3:7), then the mixed positive electrode active material, the conductive carbon black as the conductive agent and the polyvinylidene fluoride as the binder are mixed according to the weight ratio of 96:2:2, N-methyl pyrrolidone is added, and the mixture is uniformly stirred under the action of a vacuum stirrer to obtain positive electrode slurry, wherein the solid content of the positive electrode slurry is 72 wt%; uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil; drying the aluminum foil at 85 ℃, then carrying out cold pressing, cutting into pieces, slitting, and drying for 4h at 85 ℃ under a vacuum condition to obtain the anode.

The positive electrode active materials of examples 45 to 55 are shown in table 5.

(2) Preparation of the negative electrode

Mixing the negative active material artificial graphite, the conductive agent conductive carbon black, the thickening agent sodium carboxymethyl cellulose and the binder styrene butadiene rubber according to the weight ratio of 96:1.5:0.5:2.0, adding deionized water, and obtaining negative slurry under the action of a vacuum stirrer, wherein the solid content of the negative slurry is 54 wt%; uniformly coating the negative electrode slurry on a copper foil of a negative electrode current collector; and drying the copper foil at 85 ℃, then carrying out cold pressing, cutting and slitting, and drying for 12h at 120 ℃ under a vacuum condition to obtain the cathode.

(3) Preparation of the electrolyte

Mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC being 30:50:20 in an argon atmosphere glove box, adding an additive, dissolving and fully stirring, and adding lithium salt LiPF₆And mixing uniformly to obtain the electrolyte. Wherein, LiPF₆The concentration of (2) is 1.0 mol/L. The kinds and contents of the additives of examples and comparative examples are shown in tables 1 to 4, and the additive amounts shown in tables 1 to 4 are percentage contents by weight of the electrolyte.

(4) Preparation of the separator

A16 μm thick polyethylene separator was used.

(5) Preparation of lithium ion battery

Stacking the anode, the isolating film and the cathode in sequence to enable the isolating film to be positioned between the anode and the cathode to play an isolating role, and then winding to obtain a bare cell; and (3) after welding a tab, placing the bare cell in an outer packaging foil aluminum-plastic film, injecting the prepared electrolyte into the dried bare cell, and performing vacuum packaging, standing, formation (charging to 3.3V at a constant current of 0.02C and then charging to 3.6V at a constant current of 0.1C), shaping, capacity testing and other processes to obtain the soft package lithium ion battery.

Test method

(1) High temperature cycle test

And (3) placing the lithium ion battery in a constant temperature box at 45 ℃, and standing for 30 minutes to keep the temperature of the lithium ion battery constant. Charging the lithium ion battery reaching the constant temperature with a 1C constant current until the voltage is 4.2V, and then charging with a 4.2V constant voltageThe current is 0.05C, then the lithium ion battery is discharged with a constant current of 1C until the voltage is 2.8V, the current is the first cycle, the discharge capacity of the first cycle is recorded, and the thickness H of the lithium ion battery is tested₁. The lithium ion battery was subjected to 500 cycles under the above conditions, and the discharge capacity at the 500 th cycle and the thickness H of the lithium ion battery at this time were recorded₂. And respectively calculating the capacity retention rate and the thickness expansion rate of the lithium ion battery after 500 cycles according to the following formulas.

The capacity retention after cycling was calculated as follows: capacity retention after cycling ═ 100% (discharge capacity corresponding to cycling/discharge capacity of the first cycle).

The thickness expansion rate after the cycle was calculated as follows: thickness expansion ratio ═ H₂-H₁)/H₁×100％。

(2) High temperature storage Performance test

And (3) placing the lithium ion battery in a constant temperature box at 25 ℃, and standing for 30 minutes to keep the temperature of the lithium ion battery constant. Discharging to 2.8V at constant current of 0.5C, charging to 4.2V at constant current and constant voltage of 0.5C, and standing for 30 min. The fully charged battery was placed in a 60 ℃ incubator and stored for 90 days to observe the thickness change. Thickness increase rate ═ (thickness after storage-initial thickness)/initial thickness × 100%.

(3) Liquid retention amount

And (3) placing the lithium ion battery in a constant temperature box at 25 ℃, and standing for 30 minutes to keep the temperature of the lithium ion battery constant. Charging to 4.2V at constant current and constant voltage of 0.2C, and then discharging to 2.8V at constant current of 0.2C, which is the first cycle, and recording the discharge capacity of the ion battery.

Discharging a lithium ion battery to 2.8V at a constant current of 0.1C, weighing the weight of the battery to be m0 (unit g), then disassembling the battery, quickly putting the disassembled bare cell and the outer packaging foil aluminum-plastic film into high-purity acetonitrile (the purity is more than or equal to 99.9 percent) for extraction, drying the extracted bare cell and the outer packaging foil aluminum-plastic in a vacuum oven, weighing the total mass to be m1 (unit g), and weighing the electrolyte mass (g) in the lithium ion battery to be m0-m 1.

The liquid retention amount was calculated as follows: the battery capacity is equal to the mass (g) of the electrolyte in the lithium ion battery/the discharge capacity (Ah) of the lithium ion battery.

Test results

Table 1 shows electrolyte parameters and electrical performance test results of the lithium ion batteries of examples 1 to 16 and comparative examples 1 to 3.

TABLE 1

It can be seen from comparing examples 1 to 16 with comparative examples 1 to 3 that the addition of the heterocyclic compound and the additive a to the electrolyte can effectively improve the cycle capacity retention rate of the lithium ion battery, reduce gas generation during the cycle, and improve the high-temperature storage performance. The additive A is mainly attributed to the combined action of the heterocyclic compound and the additive A, an SEI film with low impedance can be formed, a negative electrode interface is protected, and therefore high-temperature cycle performance is improved. The heterocyclic compound and the additive A have synergistic effect, so that the high-temperature cycle performance of the lithium ion battery can be effectively improved, and the storage gas generation can be reduced.

Table 2 shows the electrolyte parameters and the electrical performance test results of the lithium ion batteries of example 3 and examples 17 to 28.

TABLE 2

As can be seen from table 2, the cycle performance and the storage performance of the lithium ion battery can be further improved by further adding other additives (e.g., DTD, LiDFP, FEC) on the basis that the electrolyte contains the heterocyclic compound and the additive a. The SEI can be formed and modified on the negative electrode by other additives, so that a more excellent interface protective film is formed, and the reaction of the electrolyte on the negative electrode is relieved. Therefore, the combined use of the additives can further improve the cycle performance and the storage performance of the lithium ion battery

Table 3 shows the electrolyte parameters and the electrical performance test results of the lithium ion batteries of example 2 and examples 29 to 35.

TABLE 3

As can be seen from Table 3, the electrolyte contained an appropriate amount of Mn (PF)₆)₂Can further improve the high-temperature cycle and high-temperature storage performance of the lithium ion battery, which is mainly attributed to the fact that the electrolyte forms good interface protection on the surface of the cathode active material, and Mn²⁺Can further inhibit the dissolution of lithium manganate, and Mn is added²⁺Damage of the negative electrode can be suppressed due to a better SEI film at the time of deposition of the negative electrode.

Table 4 shows the positive electrode parameters and the electrical performance test results of the lithium ion batteries of example 1 and examples 36 to 44.

TABLE 4

As can be seen from Table 4, when the sum of the contents X% of the heterocyclic compound and the additive A is compared with the specific surface area Y m of the positive electrode active material²When the ratio (X/Y)/g is in the range of 0.01 to 7.5, the high-temperature cycle performance of the lithium ion battery can be effectively improved and the storage gassing can be reduced, mainly because the heterocyclic compound and the additive A in the electrolyte can form good interface protection and less increase the impedance. Under the action of proper X/Y and electrolyte, better lithium ion battery performance can be obtained.

Table 5 shows the positive electrode parameters and the electrical performance test results of the lithium ion batteries of example 3 and examples 45 to 55. The electrolyte composition of each lithium ion battery sample was the same as in example 3, and the electrolyte retention amount of each lithium ion battery sample was 2.3 g/Ah. The area ratio of the first particles to the second particles in table 5 was controlled by controlling the mass ratio of the first particles to the second particles.

TABLE 5

As can be seen from the comparison between example 3 and examples 45 to 55, the first particles (e.g., NCM) and the second particles (e.g., LMO) in the positive electrode material can be mixed in different ratios within a suitable range to obtain better effects under the action of the electrolyte of the present application.

Reference throughout this specification to "some embodiments," "one embodiment," "another example," "an example," "a specific example," or "some examples" means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. Thus, throughout the specification, descriptions appear, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "by example," which do not necessarily refer to the same embodiment or example in this application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although illustrative embodiments have been illustrated and described, it will be appreciated by those skilled in the art that the above embodiments are not to be construed as limiting the application and that changes, substitutions and alterations can be made to the embodiments without departing from the spirit, principles and scope of the application.

Claims

1. An electrolyte comprises an additive A and a heterocyclic compound shown as a formula I

Wherein R is₁And R₂Each independently selected from substituted or unsubstituted C₁To C₆Alkylene or substituted or unsubstituted C₂To C₆Alkenylene, wherein when substituted, the substituent is at least one of halogen, cyano or phenyl;

wherein the additive A comprises at least one compound of formula II, formula III, formula IV or formula V:

wherein R is₃Is substituted or unsubstituted C₁To C₆Wherein when substituted, the substituent is halogen;

wherein R is₄、R₅、R₆、R₇、R₈、R₉、R₁₀Each independently selected from hydrogen, halogen, substituted or unsubstituted C₁To C₆Alkyl, substituted or unsubstituted C₂To C₆Alkenyl, substituted or unsubstituted C₂To C₆Alkynyl, substituted or unsubstituted C₆To C₁₀Aryl, wherein when substituted, the substituent is halogen;

wherein m is 1 to 6.

2. The electrolyte of claim 1, wherein the heterocyclic compound comprises:

at least one of;

wherein the additive A comprises at least one of methylene methanedisulfonate, propenyl-1, 3-sultone, 1, 3-propanesultone, 1, 3-propanedisulfonic anhydride, or 1, 4-butanesultone;

wherein the weight percentage of the heterocyclic compound is 0.01-6% and the weight percentage of the additive A is 0.01-6% based on the weight of the electrolyte.

3. The electrolyte of claim 1, wherein the additive a is present in an amount of α% by weight and the heterocyclic compound is present in an amount of β% by weight, based on the weight of the electrolyte, satisfying 0.02 ≦ α + β ≦ 10, 0.01 ≦ α/β ≦ 20.

4. The electrolyte of claim 1, wherein the electrolyte further comprises at least one of additive B, additive C, additive D, additive E, or additive F,

wherein the additive B comprises at least one of vinylene carbonate, fluoroethylene ester, vinyl ethylene carbonate, 1, 3-dioxane, 1, 4-dioxane, or dioxolane;

wherein the additive C is vinyl sulfate;

wherein the additive D comprises at least one of succinonitrile, glutaronitrile, adiponitrile, 2-methyleneglutaronitrile, dipropylacrylonitrile, 1,3, 6-hexanetricarbonitrile, 1,2, 6-hexanetricarbonitrile, 1,3, 5-pentanedinitrile, 1, 2-bis (cyanoethoxy) ethane, or ethoxy (pentafluoro) cyclotriphosphazene;

wherein the additive E comprises one of lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium bisthiooxalato borate, lithium difluorooxalato borate, lithium difluorophosphate, lithium tetrafluoroborate, or lithium 2-trifluoromethyl-4, 5-dicyanoimidazorate;

wherein the additive F comprises at least one of succinic anhydride, glutaric anhydride, citraconic anhydride, maleic anhydride, methylsuccinic anhydride, 2, 3-dimethylmaleic anhydride or trifluoromethylmaleic anhydride,

based on the weight of the electrolyte, the weight percentage of the additive B is 0.01-15%, the weight percentage of the additive C is 0.01-5%, the weight percentage of the additive D is 0.1-10%, the weight percentage of the additive E is 0.01-5%, and the weight percentage of the additive F is 0.01-5%.

5. The electrolyte of claim 1, further comprising a cyclic ester and a chain ester, the cyclic ester and the chain ester being present in a weight ratio of 1:9 to 7:3,

wherein the cyclic ester comprises at least one of ethylene carbonate, propylene carbonate, gamma-butyrolactone, ethylene carbonate substituted with a fluorine-containing group, or propylene carbonate substituted with a fluorine-containing group;

wherein the chain ester comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, fluoro ethyl methyl carbonate or fluoro ethyl propionate.

6. An electrochemical device comprising a positive electrode including a positive electrode active material layer and a positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material; and an electrolyte as claimed in any one of claims 1 to 5.

7. The electrochemical device of claim 6, wherein the electrolyte further comprises Mn²⁺Wherein the Mn is based on the weight of the electrolyte²⁺The weight percentage of (B) is less than or equal to 2000 ppm.

8. The electrochemical device according to claim 6, wherein the liquid retention amount of the electrolyte is 0.5g/Ah to 5 g/Ah.

9. The electrochemical device according to claim 6, wherein the sum X% of the weight percentages of the heterocyclic compound and the additive a and the specific surface area Y m of the positive electrode active material²The ratio of/g satisfies 0.01-7.5 of X/Y.

10. The electrochemical device according to claim 6, wherein the positive active material layer comprises first particles, and the positive sag is measured using a scanning electron microscopeThe spherical gray scale of the first particles is more than or equal to 115RGB (red, green and blue) and the cross-sectional area of the first particles is less than 20 mu m²The area of the first particles accounts for 5 to 50% of the cross-sectional area of the positive electrode active material layer.

11. The electrochemical device according to claim 10, wherein the positive active material layer comprises second particles, a cross section of the positive electrode perpendicular to the current collector is tested by scanning electron microscopy, the spherical gray scale of the second particles is less than 115RGB, and the cross-sectional area of the second particles is greater than 20 μm²The area of the second particles accounts for 5 to 50% of the cross-sectional area of the positive electrode active material layer.

12. The electrochemical device of claim 11, wherein the first particles comprise Li_aNi_xCo_yMn_zM_mO₂Wherein a is more than or equal to 0.9 and less than or equal to 1.2, x is more than or equal to 0.3 and less than or equal to 1, Y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, x + Y + z is more than or equal to 1, and M is more than 0 and less than or equal to 0.1, and the M element comprises at least one of Al, Ti, W, Zr, Nb, In, Ru, Sb, Sr, Y and F; the second particles contain Li_bMn_2-jMe_jO₄Wherein B is more than or equal to 0.9 and less than or equal to 1.2, j is more than 0 and less than 0.1, and the Me element comprises at least one of Mg, Ti, Cr, Al, B, Fe, Zr, Na and S.

13. The electrochemical device according to claim 12, wherein the doping amount W of Me is 0% < W < 0.7% based on the weight of the positive electrode active material.

14. An electronic device comprising the electrochemical device of any one of claims 6-13.